Programme 1: Investigating the role of sulfatides and their premetabolites on prion disease models.
Background Prion disease susceptibility and disease modification is known to be controlled by genetic factors. The main susceptibility factor and modifier of sporadic Creutzfeldt-Jakob disease (sCJD) is the PRNP codon 129 genotype. We lead a global effort to identify these genes with over 5500 samples from patients with sCJD, contributed from Europe, the US and elsewhere. We proposed STX6 and GAL3ST1 as risk genes for sCJD. Our main aim now is to understand how these risk factors work.
In this proposal we seek to investigate the importance of a new mechanism in prion diseases, underpinned by genetic evidence: sulfatide metabolism. Sphingolipids are a major class of membrane lipids. Sulfatide, a dominant component of the myelin sheath in the nervous system is synthesised by the cerebroside sulfotransferase (CST) enzyme. A common amino acid variant (V29M) of the sole enzyme involved in the synthesis of sulfatide (GAL3ST1 gene) confers an increased risk of the most common prion disease sCJD. Genetic association implies a causal association between sulfatide metabolism and neurodegeneration.
In this PhD proposal we will establish an assay for sulfatides, to measure sulfatide and other sphingolipid metabolite concentrations in biofluids and tissues of patients with prion and other neurodegenerative disorders, determine a direction of effect of the V29M polymorphism of CST on enzyme activity in model systems, and to test hypotheses about the effects of modification of this pathway on propagation of prions and other proteopathic seeds in cellular and animal models (knockout of CST in mouse already exists). We have evidence that the protective polymorphism at this enzyme acts to reduce expression, making CST a potential therapeutic target. In a 3 month rotation project we might pilot assays to test the effects of sulfatide on prion replication in cellular or cell free amplification assays, or a biophysical interaction between sulfatides (or premetabolites) and prion protein. This should be discussed with Prof Simon Mead to get an up to date status of the project.